Main page: Asteroids (theoretical models)
Earth-like life is impossible without water. Majority of asteroids that intersect Earth orbit have only limited amounts of water. However, NASA's Dawn spacecraft have surprised us all by finding water both on Ceres and Vesta.
The facts Edit
Dawn have found clear evidence of water on Ceres and Vesta. For Ceres, we know about the existence of some bright spots. Data suggests that these spots are in fact made of clay that contains solid water. The surface of Ceres is covered with dry material, but beneath it, there is a mixture of clay and ice. At the bottom of large craters (like Occator), this clay is visible and is more white then the rest of the surface. The presence of many white spots over a large area suggests that there is a global layer of icy clay beneath the crust. Scientists believe that Ceres originated somewhere further away from the Sun and then it moved inside the asteroid zone. Then, matter from falling meteorites created a new layer, covering the old white material. Sometimes, water from the clay, heated by the sun, sublimates and creates a tenuous atmosphere, that escapes fast into the space.
On Vesta, Dawn returned other shocking images. Inside some craters, the probe showed the existence of small valleys, created by water erosion, ending with sediment deposits. The explanation is that, somewhere beneath the surface, there is ice. After a meteorite impact, ice heats up and starts flowing as water inside the newly formed crater. The process does not last long, because ice sublimates fast, but the erosion signs remain. The most accepted idea is that ice was brought by comets and was blocked beneath the surface.
We can suppose that many other asteroids have water beneath their surface.
Technical conditions Edit
If an asteroid has ice, it can be more easy to be paraterraformed. However, this ice might contain salts, heavy metals and other chemical compounds that are toxic for Earth life. Water will need to be purified. Distillation can be the cheapest and fastest process.
In the Asteroid Belt, temperatures are low, below freezing point, so that a limited greenhouse effect is needed in order to keep temperatures suitable for life. Solar radiation is high enough, so that artificial heating might not be needed. Solar radiation is still enough for plant life. If we think that on Earth about 36% of light receives us and the rest is blocked by the atmosphere, we can understand that without an atmosphere there will still be enough light for plants to grow and for solar panels to work.
Without a magnetosphere and an ozone layer, asteroids are exposed to both UV and cosmic radiation. Blocking the ultraviolet light is easy, we are doing this already on Earth. For cosmic radiation and solar storms, protection is harder to maintain. Majority of plants used in agriculture have a short life cycle, so they will not live enough to suffer mutations. Humans and animals can hide beneath the crust.
The day-night cycle is usually of 11 hours, much shorter then on Earth. As possible, humans should adapt to a two-day cycle.
What use can future settlers have from rocky asteroids with water ice? They can be good places for future cities. They can become residential land, agricultural land or they can host industry.
A Residential Asteroid would probably look like a city, with buildings both on surface and underground. They will also have large greenhouses, where plants will be grown to feed the population, provide oxygen and refresh water. Residential asteroids can support office spaces for industrial corporation or they can be built for elders. Workers on industrial asteroids, after reaching a certain age, will no longer be able to work and will retire and move to a residential place. Residential asteroids can be good places for high schools and future universities.
An Agricultural Asteroid will be a place created for food and oxygen production. In some places, settlers will have limited resources. For example, asteroids close to their parent star (like Vulcanoids, see Vulcanoid Paraterraforming), are rich in metals and lack of water. In other places, like in the Oort Cloud, the lack of luminosity makes plant life impossible without artificial light and heat. Many orbital stations will also have limited space and will not be able to support plant life. Agricultural asteroids will provide food and oxygen to all these places. Unmanned cargo ships will transport food, liquid oxygen and maybe also clean water to remote industrial and trade centers. Then, those ships will return with carbon dioxide, excrements and other organic materials to be recycled.
An Industrial Asteroid (see Industrial colonization) is home to industrial corporations. Asteroids close to the Sun (or their host star) have no or almost no water and gasses. Asteroids that have water, on the other hand, are expected to have lesser amounts of high quality ores. Further away from the Sun and its devastating solar winds, at a lower temperature and with enough water to support plant life (and food for all workers), bodies from the main Asteroid Belt are very good for industrial corporations. Ores from mining asteroids will come here to be purified. Then, in other places, many goods will be manufactured, including electronics, machinery and many other things. It is possible, that at some point, a toy factory will own an asteroid, a computer manufacturer will own another one and a designer for clothes will set home to a third asteroid.
Asteroids have the advantage of low gravity. All goods can be shipped more easy. With our current technology, ships will only need a limited use of their expensive chemical engines to detach from the surface. Then, once they are at a safe distance, they can rely on more efficient ion engines or solar sails. Shipping goods between asteroids will require much time, years, but the costs will be small and the ships can be used again. By comparison, shipping goods between the 4 large moons of Jupiter is impossible without the use of chemical engines to break each moon's gravity. To escape gravity of a large moon or a planet, a chemical rocket needs to be made of multiple stages, the bottom stage being destroyed after launch.
Over time Edit
Main article: Future races
Over time, people will get adapted to the low gravity of an asteroid. Children born in low gravity will find it hard, if not impossible, to support gravity of a planet. At some point in the future, the new, Cosmic Race, will have its large network of asteroids and stations throughout the Solar System, while the classic race will be living on planets and large moons.